The existing cooker circuit is 6mm² on a B40. The customer wants to replace the free-standing cooker with 2 built-in ovens and an induction hob. Will each cable from cooker outlet to device need to be the full 6mm², (e.g HO7RN-F) or can I get away with anything smaller and more convenient (e.g. what's supplied with each oven/hob, if anything)? The final purchasing choice hasn't been made yet, so I don't know whether any of the devices will be suitable for a 13A plug/FCU, which can obviously accept a smaller cable.
I guess the thing I'm not getting is, if there was a L-E short at the cooker outlet then the (Sk)² of the 6mm² T&E's E conductor will be sufficient to withstand the I²t of the short circuit current, while if the the short was 2m further away at the far end of the flex 2.5mm² flex, Zs is not significantly higher, so I²t remains the same, while (Sk)² is much reduced and not sufficient. I feel I'm missing something very obvious here.
What's the size of the c.p.c in a 6mm² T&E? (answer: 2.5mm²), what's the size of all the conductors (including the c.p.c) in a 2.5mm² flex? (answer of course 2.5mm²) - does that reassure you?
I guess the thing I'm not getting is, if there was a L-E short at the cooker outlet then the (Sk)² of the 6mm² T&E's E conductor will be sufficient to withstand the I²t of the short circuit current, while if the the short was 2m further away at the far end of the flex 2.5mm² flex, Zs is not significantly higher, so I²t remains the same, while (Sk)² is much reduced and not sufficient. I feel I'm missing something very obvious here.
What's the size of the c.p.c in a 6mm² T&E? (answer: 2.5mm²), what's the size of all the conductors (including the c.p.c) in a 2.5mm² flex? (answer of course 2.5mm²) - does that reassure you?
